Aqueous dispersions and process of making same



Patented -Detail), 1929 isa-176 LESTER xmscnnaann, or LEONIA, NEW JansenAQUEOUS DISPEBSIONS AND PROCESS OF MAKING SAME Ho Drawing.

undergoing dispersion together with a certain quantity of materialfunctioning as a dispersin medium. In actual commercial practice, a argebulk supply of finished product is constantly maintained in theapparatus of which the agitating mechanism forms a part,

and the material to be dispersed is fed to this apparatus influidcondition while a separate stream comprising an-aqueous suspensionof dispersing medium is simultaneously led into the mass undergoingagitation, suitable provision being made for continuously orintermittently withdrawing the dispersed material from the apparatus.

In order to produce dispersions of this:

character which shall be capable of admixture with electrolytes withoutdestroying the character of the product as a dispersion, it is essentialto employ as the dispersing agent materials or-conibinations ofmaterials which are relatively inert chemically and incapable ofentering into any reaction with or being reacted upon by the specificelectrolyte which may be proposed for admixture with the product. Itwill be appreciated in this connection, where the dispersing agent issuch '4 that a specific electrolyte may react therewith and impair ondestroy its dispersive or protective properties, that under suchconditions the dispersive agent may nolonger be able to function, withthe result that the aqueous.

t dispersed condition of the system is destroyed and the dispersion isthen said to be broken.

, For the purpose of providing dispersive media which shall berelatively inert to such action, and which possess other desirableadvantages, there have been employed certain Application filed October6, 1927. Serial No. 224,526.

organic and inorganic powders, insoluble in, though readily Wetted with,water and capable of swelling or being treated so as to swell more orless and assumea plastic condition in the presence of water. Of thisclass of materials, clays, metallic silicates and oxides, casein andother proteins, starch, etc. are examples, althou h clays aregenerallypreferred and have ound extensive application in this field,since ,they are comparatively 30 inexpensive and possess to the largestextent the inertness and other properties necessary to produce thedesired product.

It has been found that certain of these mineral powder types ofdispersive media, for instance, certain kinds of clays and metalllcoxides, are sometimes deficient in suspendmg power, so that while theyare capable of exercising their function in the production of thedispersions, they are, on the other hand, 7 more or less unable toeffect a sufliciently fine dispersion to retain the entire mass ofdispersed particles in suspension in the aqueous phase over long periodsof time, with the result that the particles gradually settle out to agreater or less extent.

Emulsions made with various types of emulsifying agents in which thedispersed particles, among other conditions, are not sufliciently fine,are prone to settle out. It is 30 sometimes diflicult to secure finedispersion either because of the type of emulsifying agent used, theviscosity of the mass, temperatures, character of equipment, or thelike. The purpose of the present invention is to se treat dispersionswhich have been made, or are being made under such unfavorable con-'ditions as might impair their suspendability, in such a manner as torender them suspendable despite their large particle size.

The present invention is particularly concerned with dispersions madewith dispersive media which are open to the foregoing obj ections, andis directed to methods of treatment whereby such dispersons may beconverted into products of improved and relatively permanentsuspendability.

The invention further comprehends methods for treating dispersive mediaof the aforesaid character and which ordinarily give rise tonon-suspendable products in such manner as to render them capable ofproducing more highly suspendable dispersions.

In its broadest aspect, the invention proceeds upon the principle offorming a cellular or gel-like structure in the dispersed product. Thelnventlon is embodied invariou s modes of procedure which arehereinafter to be deof gel which'has been found to be practical incarrying out the principles-of the inven- 'tion, and that the broadconcept is not to be regarded as restricted or limited to thisparticular type of gel.

One convenient method by which silica gels may be formed is to treat anaqueous solution of sodium silicate with ammonium chloride orhydrochloric acid whereby there is precipitated a highly gelatinous masscomposed largely of silicic acid. The character of the gel thus formeddepends upon the concentration of the silicate solution employed as wellas that of the reagent with which the silicate is treated to form thesilica gel.

It seems to be characteristic of silica gels as thus produced that whenthey are agitated or stirred, they are disru ted into more or lessgrainy particles distri uted in irregular and non-homogeneous fashionthroughout the mass, and, particularly when the silicate concentrationhas been relatively low, a large quantity of free water appears afterthe gel has been agitated. With high concentrations of silicate and morerigid gels, the gel 1s not destroyed although it may be broken up andthe separate portions of the rigid gels subsequently coalesce uponstanding. ()n the other hand, it has been observed that where silicagels are formed, in dispersions of the type here referred to, the gelleddispersion thereby produced, possesses the unique property of beingable-to regain its gel character upon standing quiet for a short timesubsequent to having had the gel formation thereof converted to liquidas by stirring or otherwise. This phenomenon, i. e., to liquety bystirring and reassume gel structure on standing, does not occur withsilica gels, per so, made from aqueous solutions of equal sodiumsilicate concentration.

By virtue of this peculiar behavior of dispersions having gels formedtherein, ithecomes possible to prepare such dispersions and rely uponthe gelled condition of the aqueous continuous phase to maintain thedispersed particles in suspension, even after the product has beensubjected to stirring action or similar influence whereby the gel istemporarilydissipated. since upon permitting the product to remain in aquiescent state for ling and the rapidity with which the gelling 4action takes place. Generally, the lower the hydrogen ion concentrationof the gelled dispersion, the greater the concentration of sodiumsilicate must be, and vice versa. f

In one mode of carrying out the invention, there mayfirst be prepared anaqueous dispersion of bituminous material such as steam refined Mexicanasphalt having a melting point of, say 100 to 200 E, more or less, usingordinary brick making clay as the dis persing agent. This dispersion maybeeffected in any desired manner, for instance, in accordance with the'methods disclosed in United States Letters Patent No. 1,302,810. Suchdispersion may be composed of, say, 5055%- of the asphalt, 5 to 10% ofclay dispersing agent, and the balance water. To a suitable quantity ofthe dispersion thus produced, there may be added about 1.8%, more orless, by weight of commercial 4A% sodium silicate solution. Hydrochloricacid in quantities sufficient to bring the hydrogen ion concentration toa pH value say, 3.0 to 3.8, more or less, may be then added to thesilicate treated dispersion, with. the result that a gel formation takesplace in situ in the dispersion, and this gelv structure exerts aprotective action on the dispersed particles and serves to retain themin relatively permanent suspension."

The invention .may also be carried out by a somewhat modified procedurein which the silicate treatment is applied to the dispersing agent priorto effecting the dispersion therewith. In this procedure, it ispreferable that the concentration of silicate and acid be such that nogelling takes place in the aqueous-- The concentration may delay theformation of the gel untilafter the.

dispersing action has been completed. Accordingly, illustrating such aprocedure, say 20 parts, more or less, of brick making clay may be mixedwith, say, '100 parts of water containing. say. 5 parts. more or less,

of .the commercial 44% sodium silicate soiution. Sufiicient hydrochloricacid may he then added to the mixture to bring the hydrogen ionconcentration thereof to a pH value of, say, 2.0 to 2.3. more or less.At this pH value, substantially no gelling takes place but the aqueoussuspension is of a sirupy consistency which functions efiiciently as theI water. and irreversible. Upon allowing this heavy productto stand, itassumes a gel con dition, and it may be beaten or stirred out,

if necessary, to convert the mass into a viscous body of desiredconsistency, and thereafter, by permittlng the beaten out mass to remainquiescent, the gel will reform in the mass,

as already described, and function to maintain the product insuspension.

Should it benecessary or desirable to thin out the heavy dispersion aswithdrawn from the dispersing apparatus, this may be done with water, orwith an aqueous solution of sodium silicate and hydrochloric acid, al

though in order to favor the ready formation of the silica gel in thedispersed mass, it is preferable to employ the sodium silicate solutioncontaining the hydrochloric acid. so Eor this purpose, and to thus thinout the dispersion made as above described with the silicate-treatedclay dispersing media, there may be added to the heavy dispersion anaqueous solution composed of about, 2.2% sodium silicate, more or less,acidified with hydrochloric acid to a pH value of about 3.0,

more or less. This solution may be employed in such quantities as arenecessary to bring about the desired fluidity in the product. As afurther illustration of the foregoing procedure with another materialpossessing relatively poor suspending power, a Ken tucky ball clay maybe employed as the dispersing agent. With this substance, however, -ithas been found that for more successful results it is necessary to uselower concentrations of the sodium silicate, and also to operate at' apH value different from the 3.0 to 3.5 value used inconnection with thepreceding clay, since at this value with the Kentucky clayit is moredifficult to carry on the rigid and does not beat out easily to. thedesired body and viscosity. Hence, in order to disperse a material suchas Mexican asphalt, the dispersive media may preferably comprise 20parts, more or less, of the Kentucky clay and 100 parts of watercontaining approximately 3 .parts, 'more or less, of

t the commercial 44% sodium silicate solution,

and acidified with hydrochloric acid to a pH value of, say, 6.0 to 6.5,more or less. With 'suchdispersive media, the'asphalt may be dispersedmore readilyand the gel formed in the dispersion may be easily beaten orLdispersing action and the gel formed is too.

stirred out to a homo eneous body of desired consistency, the gel eingsubsequently reformed upon allowing the product to remain quiet, and aslong as the gelled condition exists in the product, the dispersedparticles are enabled to remain in suspension. The. product as thusproduced is capable, Without any further treatment for the modificationof its pH value, of drying to a film which is highly resistant topermeation by Water.

Ammonium chloride and other equivalent materials may be used instead ofhydrochloric acid, if desired.

By the use of the term gel or gelled in the claims I intend to define anemulsion possessed of the unique property of being able to regain itsgelled character by standing quiet for a short time subsequent to havinghad the gelled formation thereof converted to liquid with a slightamount of stirring and without the use of a diluent or substantialquantities thereof. I

I claim as my invention:

1 1. An aqueous gelled'dispersion of a waterproofing material, theaqueous phase containing silica in gelled form.

2. An aqueous gelled dispersion of a Waterproofing material, the aqueousphase being in the form of a gel.

3. A product of the character described, comprising a waterproofingmaterial, dispersed in a gelled aqueous vehicle.

4. A product of the character described, comprising a dispersion, thecontinuous phase of which is in the form of a gell, the internal phaseof said dispersion comprising a waterproofing material.

5. A product of the character described, comprising a waterproofingmaterial dispersed in an aqueous vehicle, said product beingcharacterized by its ability to gel on standing.

6. A gelled product comprising a waterproofing material dispersed in anaqueous vehicle, the gel condition of said product being dispelled byagitating action, said product being characterized by its ability toreturn to the gel condition upon standing quiet after being subjected tosuch action as has been suflicient to dispel the gel condition there- 7.-A product of the character described, comprising a waterproofingmaterial dispersed in water, and containing substances for causing agelled formation in the aqueous phase thereof.

8:A product of the character described, comprising a water-proofingmaterial dis- .persed inwater, and containing substances for causing theformation of silica gel in the product. K

persedwaterproofing particles whereof tend tea settle out of suspension,the step which 9. In the production of dispersions, thedis- I comprisesforming a gel in situ in the dispersion.

10. In the production of dispersions, the dispersed waterproofingparticles whereof tend to settle out of suspension, the step whichcomprises forming a silica gel in situ in the dispersion.

11. The method of treating aqueous dispersions whereby to in creasetheability of the dispersed waterproofing particles thereof to remain insuspension, which comprises combining with the aqueous dispersionamaterial capable of inducing a gel formation in theaqueous phasethereof.

2. The method of treating dispersions whereby to increase the ability ofthe dispersed Waterproofing particles thereof to remain in suspension,which comprises comv bining with the dispersion a material capable ofinducin av silica el formation in the a: a:

dispersion,

13. In the production of dispersions, the steps which comprise combiningwith a mineral powder dispersing medica, substances capable of producinga gel formation in the dispersion, and effecting dispersion of awaterproofing material, with said combined mixture. g

In testimony whereof I afiix my signature.

' LESTER KIRSCHBRAUN.

